Get the transmission, driveshaft, rear diff, and rear axles. The stock parts should be fine for n/a builds but if you are adding lots of power they aren't made for that. Good news is Honda AWD swaps are kind of taking off and various companies are starting to offer upgrades for this stuff.
FYI there is also a billet H22 AWD bellhousing in development that will accept the B-series transfer case. This may ultimately be the best solution for AWD Preludes because using B-series transmissions requires the engine to lean forward, even with an H2B setup. The overall fit in the engine bay just isn't as good like that, having it lean back a bit like with H-series / stock engine is much better.
Here is an example of the prototype diff mount that was made for the S2k rear diff, however this idea has been scrapped:
The current idea is to only support the CR-V/Element rear diff and develop one mount that will fit on 2WS and 4WS cars. It should look very similar to this.
Currently this project is waiting on one vehicle to leave my property then I will be able to bring up the development car and make further progress on it.